1. Field of the Invention
The present invention relates to a piezoresistive strain sensing device in which diffused resistors are formed in a semiconductor single-crystal substrate. More particularly, it relates to a piezoresistive strain sensing device which is well suited to sensitively and precisely detect a stress field acting on an IC chip within a semiconductor package.
2. Description of the Prior Art
Prior art devices wherein a mechanical stress resulting from the application of a strain, is converted into an electric signal by utilizing the piezoresistance effect of a semiconductor, include, for example, a semiconductor strain sensor as disclosed in the official gazette of Japanese Patent Application Laid-open No. 56-140229. In this device, a bridge circuit is formed by diffused resistors on a diaphragm of silicon, and a strain is measured by detecting the fractional change in resistivity based on the deformation of the diaphragm attendant upon a surface strain. Another prior art device has been attempted in which a diffused resistor is formed on a silicon substrate, and the substrate is buried in a resin which acts as sensing means, thereby to detect a two-dimensional stress field acting within a surface formed with the diffused resistor. In either case, however, only the detection on a specified stress component is achieved, and the use is limited. A three-dimensional stress field exists in a general structure, and mechanical strain-electricity transducers including the prior-art semiconductor strain sensors have had the problem that the three-dimensional stress field cannot be separately detected.